Take account of bounds set on drag drawables.

If bounds are set on a compound drawable in a textview, drawing it into a
bitmap set to the intrinsic size of the drawable results in it being scaled
down in the top corner. Scaling it down again into the grid icon size then
gives a tiny icon.

Use the drawable bounds if any are set, otherwise use the intrinsic size.

Bug: 14103508
Change-Id: Idadd7bb891dc33d092eb9ceb3025b9a5d9e1bfd8